linux-kernel - Re: [patch RFC 5/5] x86/speculation: Add basic speculation control code

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Date:   Wed, 10 Jan 2018 13:35:45 -0800
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     "Van De Ven, Arjan" <arjan.van.de.ven@...el.com>,
        Andrea Arcangeli <aarcange@...hat.com>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        Jiri Kosina <jikos@...nel.org>,
        "Mallick, Asit K" <asit.k.mallick@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...uxfoundation.org>,
        "x86@...nel.org" <x86@...nel.org>, Borislav Petkov <bp@...en8.de>,
        Andi Kleen <ak@...ux.intel.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [patch RFC 5/5] x86/speculation: Add basic speculation control
 code

On 01/10/2018 05:53 AM, Van De Ven, Arjan wrote:
>> ibrs_enabled 2:
>>
>> sets IBRS always in host
> 
> this is not secure
> 
>> This matches the semantics described here by Tim patchset on lkml:
>>
>> https://marc.info/?l=linux-kernel&m=151520606320646
> 
> I will talk to Tim, it's not right.
> 
> 

Yes, there's a misunderstanding on my part.  Leaving IBRS=1 all the
time may not provide full protection on all cpu models.

Tim